Add "live" chart to homepage

package.json

@@ -48,6 +48,7 @@
     "sinon": "^1.17.2",
     "sinon-chai": "^2.8.0",
     "victory": "*",
+    "victory-chart": "^10.3.0",
     "victory-examples": "*"
   }
 }

src/screens/home/components/benefits.js

@@ -10,6 +10,7 @@ import Demo from "./demo";
 import DemoFlexible from "./demo-flexible";
 import DemoNative from "./demo-native";
 import DemoSharedEvents from "./demo-shared-events";
+import DemoLiveChart from "./demo-live-chart";
 
 class Benefits extends React.Component {
   getStyles() {
@@ -41,7 +42,7 @@ class Benefits extends React.Component {
       },
       flexItem: {
         flex: "1 0 auto",
-        margin: `${VictorySettings.gutter * 2}px 3vw 0`,
+        margin: `${VictorySettings.gutter * 2}px 1vw 0`,
         minWidth: "360px",
         textAlign: "center"
       },
@@ -83,7 +84,7 @@ class Benefits extends React.Component {
             </p>
           </div>
           <div style={styles.flexItem}>
-            <DemoSharedEvents />
+            <DemoSharedEvents/>
             <p>
               <a
                 href="https://github.com/FormidableLabs/victory-examples/blob/master/src/components/shared-events.js"
@@ -92,6 +93,16 @@ class Benefits extends React.Component {
               </a>
             </p>
           </div>
+          <div style={styles.flexItem}>
+            <DemoLiveChart/>
+            <p>
+              <a
+                href="https://github.com/FormidableLabs/victory-docs/blob/master/src/screens/home/components/livechart.js"
+              >
+                <span style={styles.smallCaps}>View source</span>&nbsp;<Icon glyph="external-link" />
+              </a>
+            </p>
+          </div>
         </div>
 
         {/* Friendly */}

src/screens/home/components/demo-live-chart.js

@@ -0,0 +1,86 @@
+import React from "react";
+import { last, mean } from "lodash";
+import LiveChart from "./livechart";
+
+export default class DemoLiveChart extends React.Component {
+  constructor(props) {
+    super(props);
+    this.period = 2000;
+    this.domain = [54.6, 55.25];
+    this.maxPoints = 30;
+    this.state = {
+      data: this.getInitialData()
+    };
+  }
+
+  nextPoint(previous = null) {
+    const [low, high] = this.domain;
+    const newPoint = low + Math.random() * (high - low);
+    return previous ? mean([previous, newPoint]) : newPoint;
+  }
+
+  getInitialData() {
+    return [
+      {x: 0, y: this.domain[0] + 0.05},
+      {x: 1, y: this.domain[0] + 0.15}
+    ];
+  }
+
+  getNewData() {
+    const data = this.state.data;
+
+    if (data.length !== this.maxPoints) {
+      // add one
+      const lastPoint = last(data);
+      data.push(
+        {y: this.nextPoint(lastPoint.y), x: lastPoint.x + 1}
+      );
+      return data;
+    } else {
+      return this.getInitialData();
+    }
+  }
+
+  componentDidMount() {
+    this.setStateInterval = setInterval(() => {
+      this.setState({ // eslint-disable-line react/no-did-mount-set-state
+        data: this.getNewData()
+      });
+    }, this.period);
+  }
+
+  componentWillUnmount() {
+    clearInterval(this.setStateInterval);
+  }
+
+  getStyles() {
+    return {
+      parent: {
+        display: "block",
+        boxSizing: "border-box",
+        margin: "0 auto",
+        padding: 0,
+        width: "auto",
+        height: "100%",
+        maxHeight: "280px"
+      }
+    };
+  }
+
+  render() {
+    const styles = this.getStyles();
+    return (
+      <svg
+        viewBox="0 0 450 350"
+        className="fancyBorder"
+        style={styles.parent}
+      >
+        <LiveChart
+          data={this.state.data}
+          period={this.period}
+          domain={this.domain}
+        />
+      </svg>
+    );
+  }
+}

src/screens/home/components/livechart.js

@@ -0,0 +1,78 @@
+import React from "react";
+import { round } from "lodash";
+import { VictoryAxis, VictoryChart, VictoryLine, VictoryScatter } from "victory-chart";
+
+const leftPad = (str, len, ch) => {
+  str = String(str);
+  let i = -1;
+  if (!ch && ch !== 0) {
+    ch = " ";
+  }
+  len -= str.length;
+  while (++i < len) {
+    str = ch + str;
+  }
+  return str;
+};
+
+const start = Date.now();
+
+const makeDate = (period, count) => {
+  const date = new Date(start + count * period);
+  const hours = leftPad(date.getHours(), 2, 0);
+  const minutes = leftPad(date.getMinutes(), 2, 0);
+  const seconds = leftPad(date.getSeconds(), 2, 0);
+  return `${hours}:${minutes}:${seconds}`;
+};
+
+const LiveChart = ({data, period, domain}) => (
+  <VictoryChart
+    animate={{ duration: 1000 }}
+    padding={{
+      left: 80,
+      right: 50,
+      top: 20,
+      bottom: 30
+    }}
+  >
+    <VictoryAxis
+      tickFormat={makeDate.bind(null, period)}
+      tickCount={3}
+      style={{
+        ticks: {stroke: "black", strokeWidth: 3}
+      }}
+    />
+    <VictoryAxis dependentAxis
+      label="Price"
+      tickCount={4}
+      tickFormat={(y) => round(y, 2)}
+      domain={domain}
+      style={{
+        axisLabel: {
+          padding: 50
+        },
+        ticks: {stroke: "black", strokeWidth: 3}
+      }}
+    />
+    <VictoryLine
+      data={data}
+      interpolation="monotoneX"
+      style={{
+        data: { strokeWidth: 1 }
+      }}
+    />
+    <VictoryScatter
+      data={data}
+      size={5}
+      style={{
+        data: {
+          fill: "black",
+          stroke: "white",
+          strokeWidth: 3
+        }
+      }}
+    />
+  </VictoryChart>
+);
+
+export default LiveChart;